Added pre query string middleware function so users can run there own query string logic before ocelot does its mappings

src/Ocelot/Middleware/OcelotMiddlewareConfiguration.cs

@@ -34,5 +34,11 @@
         /// This allows the user to completely override the ocelot authorisation middleware
         /// </summary>
         public Func<HttpContext, Func<Task>, Task> AuthorisationMiddleware { get; set; }
+
+        /// <summary>
+        /// This allows the user to implement there own query string manipulation logic
+        /// </summary>
+        public Func<HttpContext, Func<Task>, Task> PreQueryStringBuilderMiddleware { get; set; }
+        
     }
 }

src/Ocelot/Middleware/OcelotMiddlewareExtensions.cs

@@ -90,6 +90,9 @@ namespace Ocelot.Middleware
             // Now we can run any header transformation logic
             builder.UseHttpRequestHeadersBuilderMiddleware();
 
+            // Allow the user to implement their own query string manipulation logic
+            builder.UseIfNotNull(middlewareConfiguration.PreQueryStringBuilderMiddleware);
+
             // Now we can run any query string transformation logic
             builder.UseQueryStringBuilderMiddleware();